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MF70 Brushless Conversion


The Proxxon MF70 micro milling machine is an outstanding - for its price - hand controlled milling machine.

Converting it to a full blow CNC machine is fairly easy and is covered extensively on  YouTube and also Googling "MF70 CNC conversion" gives plenty of options.

Less common is the upgrading of the spindle motor to a brushless version.  The standard MF70 has a brushed 125W motor which is almost impossible to repair or replace and when our machine started malfunctioning our only choice was to replace the motor with a brushless version. 


Here's what we did :

 Proxxon MF70 Brushless motor

1. Unplug motor mains lead. Remove top cover and cable clamp.

2. Undo the two M3 hex bolts holding the motor down and pull the motor out - the spindle is a push fit into the main spindle bearing.

3. There is a small gear attached to the motor spindle which can be removed but we decided to dispose of it since there is no fixing screw.

4. Remove the slotted plate under the motor and THROW everything else away including the electronics, switch, motor.

5.; Source the following : a 12V brushless motor with a 4mm spindle (We used a NTM Prop Drive Series 35-42A 1250Kv 600W from HobbyKing), a TREX 450 pinion gear, a servo tester, a Controller (TURNIGY TRUST 70A SBEC Brushless Speed Controller) and a 30A 12v power supply.   We have found that 600W is more than adequate for cutting silver. gold and wax.  In fact, we initially used a 250W motor.  The one we chose runs fast 24000 rpm @ 12V and uses less than 300W when running and it runs cool, but whiny!

6. Drill out pinion to 4mm and cut off about 3mm from the end of the motor shaft - this is not critical.

7. Place two M3 bolts in outer fixing holes on slotted plate. Fit the slotted plate to the motor using M3 hex bolts - getting it central is tricky but essential. Tighten fully.

8. Push pinion onto motor shaft leaving about 1mm gap at the end - not critical.

9. Push assembled motor into the bearing assembly and tighten the two M3 bolts placed previously.

10. Wire up the controller and servo test box. Fix Servo test box to outer casing with M2.5 bolts. Replace top cover.

11. Power up and enjoy your Proxxon MF70 powered by a helicopter motor - just make sure it is held with decent bolts!


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